1. Field of the Invention
The present invention relates to a perpendicular magnetic recording head for recording data on a recording medium, e.g., a disk having a hard surface, by applying a perpendicular magnetic field. In particular, it is an object of the present invention to provide a perpendicular magnetic recording head capable of suppressing an occurrence of fringing in a recording pattern and improving a recording efficiency.
2. Description of the Related Art
A perpendicular magnetic recording head by using a perpendicular magnetic recording system is a device for recording magnetic data on a recording medium, e.g., a disk, with a high density. A general structure of this perpendicular magnetic recording head is configured to include an auxiliary magnetic pole layer made of a ferromagnetic material and a main magnetic pole layer made of a ferromagnetic material and disposed leaving a space to this auxiliary magnetic pole layer.
A front end of the above-described auxiliary magnetic pole layer and a front end of the above-described main magnetic pole layer appear on a facing-surface opposed to the recording medium and are magnetically coupled to each other at the rear in a height direction. A coil layer is disposed in between the above-described auxiliary magnetic pole layer and the above-described main magnetic pole layer. When a recording magnetic field is induced to the above-described auxiliary magnetic pole layer and the above-described main magnetic pole layer through energization of this coil, a leakage recording magnetic field is generated in between the above-described auxiliary magnetic pole layer and the above-described main magnetic pole layer on the facing-surface opposed to the recording medium, this leakage recording magnetic field passes through the recording medium and, thereby, a recording signal is recorded on the recording medium.
Here, the ferromagnetic material used for the main magnetic pole layer has a high saturation magnetic flux density, but in general, the magnetic permeability is low. Therefore, the recording magnetic field induced to the main magnetic pole layer is difficult to induce to the front end of the above-described main magnetic pole layer. Consequently, there is also a perpendicular magnetic recording head in which a yoke layer made of a material having a large magnetic permeability is disposed in contact with the above-described main magnetic pole layer with the intention of inducing the recording magnetic field easily to the front end of the main magnetic pole layer.
In the perpendicular magnetic recording head including the yoke layer disposed as described above, it is effective to bring the above-described yoke layer close to the facing-surface opposed to the recording medium in order to effectively induce the recording magnetic field to the front end of the main magnetic pole. However, if the above-described yoke layer is excessively brought close to the facing-surface opposed to the recording medium, a recording magnetic field tends to also flow from the front end of this yoke layer and, thereby, a so-called side fringing problem occurs.
A perpendicular magnetic recording head, in which a front-end surface 35a of a yoke layer is formed from a sloped surface or a curved surface that approaches a facing-surface opposed to a recording medium with increasing proximity to an upper surface from a lower surface, is disclosed in FIG. 3 and FIG. 14 of U.S. Pat. No. 6,687,084 as a perpendicular magnetic recording head capable of suppressing such a side fringing problem, while another type of sloped surface or curved surface is also disclosed in FIG. 1 and FIG. 10.
In the perpendicular magnetic recording head disclosed in U.S. Pat. No. 6,687,084, since the yoke layer 35 made of a material having a large magnetic permeability is disposed in contact with a main magnetic pole layer 24, a recording magnetic field can be induced to the front end of the main magnetic pole layer 24. Furthermore, since the front-end surface 35a of the above-described yoke layer 35 is formed as a sloped surface or the like and the cross-sectional area is decreased, the magnetic volume of the yoke layer 35 is reduced in the neighborhood of the facing-surface opposed to the recording medium. Therefore, flowing of the recording magnetic field from the front-end surface of the yoke layer 35 to the recording medium can be suppressed and, thereby, an occurrence of side fringing can be suppressed.
In the perpendicular magnetic recording head disclosed in the above-described U.S. Pat. No. 6,687,084, a region in which the front-end surface 35a of the yoke layer 35 is disposed is formed in such a way that the thickness dimension is increased continuously toward the rear in the height direction. However, the height dimension is constant on the side behind the front-end surface 35a in the height direction. Furthermore, it is not clear whether the width dimension from the upper surface toward the lower surface of the above-described yoke layer 35 is constant or not. In the region in which the film thickness of the front-end surface of the above-described yoke layer is varied (inclined), it is not clear from the descriptions with respect to FIG. 1, FIG. 10, and the like whether the width dimension is varied in relation to the film thickness.
Therefore, the above-described yoke layer 35 in U.S. Pat. No. 6,687,084 is unsatisfactory to effectively induce the recording magnetic field to the main magnetic pole layer 24, since there is a limit in increasing the magnetic volume as a whole.